Such devices comprising in particular two probes emitting and collecting ultrasound waves are already known, in particular from documents FR 2 234 545 and U.S. Pat. No. 6,634,233. These ultrasound waves are emitted in pulsed form by the probes, are propagated through an appropriate medium and are reflected by an internal or external surface of the object being studied. These reflected waves then return to a sensor which then generates a signal from which is measured a travel time of the waves in the medium between their emission and their reception after reflection. This travel time, knowing the speed of propagation of the waves in the medium, can be used to calculate the position of the reflection points.
Such devices are normally used to measure the internal and external diameters of a tube and/or the thickness of the wall of such a tube.